Sheet handling systems, including in particular document handling systems for transporting members bearing indicia to and from imaging stations, are well known. Generally, document handlers have a defined path into which documents held in a tray or input area are drawn and transported to an image processing station, for example, an image input terminal. Document handlers, also generally, provide a path through which the documents are withdrawn from the image processing station.
Reciprocating document handling systems of the type to which this invention relates are those in which, in at least some instances, documents are directed in the opposite direction from others of those transported in the document handling system. That is, for example, documents entering a processing station pass over or under, depending on the construction of the defined paths, the documents exiting the processing station.
In the past, devices of this type have been usually operated at sufficiently slow speed (e.g., approximately 30 documents per minute) so that little or no overlap of the documents entering and exiting the processing station occurred. However, as seemingly the case with all devices, there exists the need and desire to increase the speed of these document handlers. One approach is to simply increase the speed of operation by having a high throughput rate e.g., of 60 documents per minute. However, such an increase in speed would require document exchange times on the order of 400 milliseconds or less. Further, due to the reciprocation of the belt, the acceleration and deceleration of the belt are critical constraints. Thus, there exists a need to permit greater overlap of the documents in such reciprocating document handlers without the attendant problems of smearing, stubbing, improper registration, jamming, and the like so that the throughput rate of document increase is not only a function of increasing the speed of document travel.
The following patents may be of relevance to the present invention:
U.S. Pat. No. 4,627,709 PA0 Patentee: Kitajima et al. PA0 Issued: Dec. 9, 1986 PA0 U.S. Pat. No. 4,469,319 PA0 Patentee: Robb et al. PA0 Issued: Sep. 4, 1984 PA0 U.S. Pat. No. 4,884,794 PA0 Patentee: Dinatale et al. PA0 Issued: Dec. 5, 1989 PA0 U.S. Pat. No. 4,353,541 PA0 Patentee: Parzygnat PA0 Issued: Oct. 12, 1982
U.S. Pat. No. 4,627,709 discloses an automatic document handler for feeding documents to an image processing station to record the information on the document. The handler includes a belt, which is operable in two directions and which is urged into position by backup rollers. The belt is provided for transporting the documents onto and off of a platen. Apparatus is also provided for inverting the transported documents so that the information on both sides of the document may be recorded.
U.S. Pat. No. 4,469,319 discloses a document handler having rollers which engage a document to transport across a platen. The rollers are actuable to lift them so that the loading force on documents on the surface of the platen is reduced.
U.S. Pat. No. 4,884,794 discloses a reciprocating, recirculating document handler for feeding documents to an image processing station to record the information on the document. The handler includes a belt, which is operable in two directions and which is urged into position by backup rollers. The belt is provided for transporting the documents onto and off of a platen. Apparatus is also provided for inverting the transported documents so that the information on both sides of the document may be recorded and for permitting recirculation of the documents in a simplex and duplex manner.
U.S. Pat. No. 4,353,541 discloses a copier document handling apparatus for feeding documents to and from a registration position at an imaging station of a copier with reversible direction of the belt feed at the station. A pressure roller is disposed above a surface of the belt to urge the belt into closer engagement with the surface. The pressure roller is actuated by the action of the belt so that when feeding document the registered position at the imaging station the pressure of the roller on the belt is decreased relative to the higher pressure exerted on the belt as a document is urged from the station.
In accordance with one aspect of the present invention, there is provided a document handling apparatus for transporting documents to and from a processing station, which comprises means for moving a first document to the processing station and a second document from the processing station with a portion of the first document being in sliding contact with a portion of the second document and the first document moving in a direction opposed to the direction of movement of the second document. The moving means of this apparatus can comprise a belt transport adapted to move in a first direction to move the first document to the processing station and in a second direction opposed to the first direction, to move the second document from the processing station. Further, the process station may comprise a platen, and the belt transport may comprise a belt positioned adjacent the platen and also comprise means for urging at least a portion of said belt toward the platen with the documents being adapted to be interposed between the belt and the platen.
The apparatus according to this aspect of the invention can further include comprises a movable pressure member adapted to move in a first direction to urge the belt toward the platen and in a second direction, opposed from the first direction, to reduce the force being applied on the belt. The urging means according to this aspect of the invention may comprise a stationary pressure member adapted to press the belt against the platen defining a nip therebetween with the document entering the processing station and exiting the processing station at a common marginal region of the nip. In further accordance with this aspect of the invention, the pressure member may also comprise a roller and means for moving the roller in the first direction to increase the force applied on the belt and in the second direction to decrease the force applied on the belt, or the pressure member may comprise a gravity biased roller and an actuating device for lifting the roller away from the belt to reduce the force being applied on the belt. According to this aspect of the invention, documents transported in the first direction engage the belt and documents transported in the second direction exit the belt, such that the documents slide substantially freely relative to one another. The invention may also include positioning the urging means proximate a marginal region of the belt with the documents being adapted to be moved toward the marginal region of the belt and away from the marginal region of the belt.
Pursuant to another aspect of the present invention, there is provided a method for exchanging documents exiting and entering a transport belt at an exchange area in a first direction and a second opposite direction, respectively. This method comprises the steps of: rotating a transport belt in the first direction; urging the leading edge of a document exiting the transport belt to continue in the first direction; directing a second document to the belt in a second direction; reversing the direction of the transport belt to engage and transport the second document in the second direction; engaging sides of the first and the second documents at the exchange area; and relieving the bearing pressure of the transport belt proximate the exchange area to promote the free sliding of the engaged sides of the first and the second documents at the exchange area. The method may also include the step of: engaging the first document in a driving roll nip as part of the urging step; actuating a pressure roll for bearing on the belt transport from a position adjacent the belt transport to a position away from the belt transport as part of the relieving step; and returning the pressure member to its position adjacent the belt transport after said engaging step.
Pursuant to yet another aspect of the invention, a reciprocating document handler for transporting documents to and from a processing station comprises a belt transport for transporting documents entering the processing station in a first direction and exiting the processing station in a second direction, opposed to said first direction, means for reducing pressure exerted on documents entering and exiting the processing station, and means for directing one document onto the belt transport substantially concurrently with another document leaving the belt transport. The document handler of this aspect of the invention may further comprise means for driving the other document in the second direction as the one document is directed onto said belt transport, and the reducing means of the document handler may include an actuable pressure member supported proximate an area of the belt transport where the transported documents enter the process station and the transported documents exit the process station.